<template>
   <div id="app">
    <div>
      <p>请选择你要购买的书籍</p>
      <ul >
        <li v-for="(item,index) in arr" :key="index">
          {{item.name}}
          <button @click="add(index)">买书</button>
        </li>
      </ul>
      <table border="1" width="500" cellspacing="0">
        <tr>
          <th>序号</th>
          <th>书名</th>
          <th>单价</th>
          <th>数量</th>
          <th>合计</th>
        </tr>
         <tr v-for="(item,index) in arr" :key="index">
          <th>{{index+1}}</th>
          <th>{{item.name}}</th>
          <th>{{item.price}}</th>
          <th>{{item.count}}</th>
          <th>{{item.price * item.count}}</th>
        </tr>
      </table>
      <p>总价格为:{{total}} </p>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
         arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    }
  },
  methods:{
   add(index){
    this.arr[index].count++
   },
  },
  computed:{
    total(){
   return this.arr.reduce((t,c)=> t + c.price *c.count,0)
}
  }
}
</script>